Induction motors known as solid rotor machines include a stator and a solid steel rotor rotatably disposed within a bore of the stator. A conductive layer may be provided on the outer operating surface of the rotor to increase the electrical conductance in the rotor. Conventional techniques of providing a copper layer on a steel rotor make use of air and electric means of propelling high-velocity molten copper against the rotor surface. Examples of such conventional techniques include blast coating and vapor deposition.
Conventional techniques do not produce adequate adhesion of the copper conductive layer to a solid core steel rotor. The copper-steel bond created by conventional techniques is not adequately strong to withstand high rotational speeds. Additionally, these techniques lead to oxidation and porosity of the copper conductive layer. Oxidation and porosity of the resulting copper conductive layer raises the electrical resistance, which necessitates a thicker conductive layer. The rise in electrical resistance increases the apparent air gap between the rotor and the stator, and leads to higher electrical losses in the motor.